The Over/Under Monorail System for Longwall Mining Operations described herein relates overhead mounted monorail systems used with underground longwall mining systems, wherein the monorail systems manage the electrical cables and hydraulic lines associated with longwall mining systems, which are commonly used in underground coal mining operations.
The longwall mining system is operated by the mine operator and is a dynamic system where, as the coal is extracted from the operating face, the entire longwall system moves. Therefore, all the support equipment must move as well. The monorail system that handles the electric cables and the hydraulic conduits is, by necessity, a dynamic system and the design of such must account for continual movement of the longwall while the electrical power and hydraulic fluid sources remain stationary and are moved only intermittently.
Due to numerous variations in geological conditions and customary designs being used at various mining operations, any system being supplied to a particular mine must be capable of a variety of physical layouts and dimensional constraints. Hydraulic fluid to and from the pumps to the longwall face is conveyed via hoses or other conduits such as pipe. The electric power from the power center to the longwall face is conveyed via electric cables.
In the early days of mechanized longwall mining system, the electrical cables and hydraulic hoses were bundled together and dragged along the mine floor by the use of pulling devices. In these days, a typical hydraulic system included 1 ea, ¾ inch pressure hose and 1 ea, 1 inch return hose. Also, the typical voltage in use was 995 volts. As the hydraulic equipment evolved and was made larger, the demand for fluid was more and larger hoses and multiple parallel hoses became common.
When the use of 2300 volts and 4160 volts came into common practice, dragging the cable along the floor was discontinued and the introduction in the use of a festooning monorail system was adopted. The use of this system avoided the need for personnel to handle power cables and kept the cables out of the moisture associated with mine floors. For several years, cables and hoses were hung from monorail trolleys that rolled along monorail beams hung from the mine roof. Increasing hydraulic demands typically required the use of up to 4 ea, 2 inch pressure hoses and 4 ea, 2½ inch return hoses. Using a greater number of hoses became difficult and the friction loss through the hoses grows more and more unacceptable.
The use of a parallel (side-by-side) pair of monorail systems next came into use. In this type of system, there is one complete monorail system to carry the electrical cables, which can typically include an overhead, e.g., roof mounted monorail, and a number of trolleys carried on the monorail, which trolleys carry the electrical cables. Additionally, there is also a second, complete monorail system to carry the hydraulics, which can typically include a second overhead, e.g., roof mounted monorail, and a number of trolleys carried on this second monorail, which trolleys carry the hydraulic conduits. A difference in this system from prior systems is that all of the hydraulic conduits were formerly hydraulic hoses, but now much of the hydraulic conduits have been replaced by the use of pipes.
Presently, there are believed to be at least a couple such systems in use where the electrics and hydraulics are handled by two separate monorail systems. This is believed to be the existing state of the art for overhead monorail systems for longwall mining operations.
Compared to earlier monorail systems, an advantage of such side-by-side monorail systems can be a more efficient distribution of the hydraulic fluid, because the hydraulic conduits, formerly hoses, are replaced by pipes. Some disadvantages to the existing side-by-side monorail systems can be that two overhead mounted monorail beams must be handled, i.e., reclaimed, transported and re-hung, as the longwall face moves, and that the side-by-side monorail systems can occupy much of the very limited space available in a typical mine entry.
Therefore, there is a need for a more space-efficient and more easily handled monorail system.